Lamp



Patented Oct. 9, 1934 LAMP George Sperti, Covington, Ky., assigner toSperti Lamp Corporation, New York, N. Y., a corporation of DelawareApplication January 25, 1932, Serial No. 588,748

8 Claims.

This invention relates to lamps of the type combining a source ofvisible radiation and an arc constituting a source of ultra-violetradiation and to an electrode for use particularly in such a 6 lamp butadapted for use in any electric arc lamp.

, In the prior application of George Sperti, Serial No. 572,394, ledOctober 31, 1931, there is disclosed a lamp embodying an outer bulbcontaining an incandescent lament which provides a 10 source of visibleradiation and an inner bulb wherein an arc is established betweensuitable electrodes in an atmosphere of ionized gas or vapor. Theresultant spectrum of such a lamp is that of the incandescent filamenthaving superimposed thereon the spectrum from the arc, the latterproviding preferably a substantial amount of energy in the ultra-violetregiorr of the spectrum. By separately enclosing the incandescentfilament and the arc, the two sources may be operated substantiallyindependently as regards conditions such as vapor or gas pressure andthe arc is prevented from striking to the filament so that it ispossible to operate the lamp successfully` at normal house lightingvoltages and currents. For such purposes, the lamp and particularly thearc element therein is entirely self-contained and requires no externalstarting or controlling devices.

As described in the aforesaid application, the arc is establishedbetween a pair of spaced electrodes and in order to render the arcself-starting, the electrodes are heated by suitable filaments and thegas or Vapor in the arc chamber is ionized to start the operation of thearc. In order to assist in this ionization, the electrodes preferablyembody one or more oxides of material such as thorium, strontium, bariumand the like which on being heated have substantial electronic emission.Since one of the necessary attributes of a lamp of this type is longlife, the electrodes must be so constituted that they do not evaporateor disintegrate at operating temperatures regardless of age. Moreover,the electrodes should be of a material which does not disintegrate anddeposit on the 45 walls of the bulb so as to cause blackening. Moreover,the electrodes should be such that the oxides referred to above are notsubjected to unnecessary disintegration during ordinary operation of thelamp but are used only for starting purposes.

One of the objects of the present invention is to provide a novel formof electrode for use in lamps of the above type or in any electric arclamp whereby the electrode is substantially non-vaporizable duringoperation and hence can be used -these electrodes are heated by means oflaments for long periods and is not harmed by prolonged operation.

Another object is to provide an electrode having an arcing surface of anoxide such as zirconium oxide on which the arc is maintainedduringnormal operation and also embodying oxides such as strontium andbarium which are effective in starting the arc but are substantially notaffected during normal operation of the arc.

Only one embodiment of the invention has been illustrated in theaccompanying drawing, but it is to' be expressly understood that saiddrawing is for purposes ,of illustration only and is not to be construedas a definition of the limits of the invention, reference being had tothe appended claims for this purpose.

In the drawing,

Fig. 1 is a perspective view of a lamp embodying the invention; and

Fig. 2 is a sectional view of a part of the lamp 75 shown in Fig. 1.

As shown in Figs. 1 and 2, the lamp embodies a bulb 1 :of any suitablesize and Shape and the usual orany suitable base 2. Where the lamp isintended to emit ultra-violet light, the bulb 1 80 should be of materialwhich transmits ultra-violet radiations of the desired wave lengths,which ordinarily will include only wave lengths longer than about 2800to 2900 Angstrom units. Sealed in the neck of the bulb is a standard 3whereby the usual conductors 4 and 5 are introduced into the bulb andwhereby the various elements are supported within the bulb. Anincandescent lament 6 is supported by means of wires 7 and 8 from thestem 3, the Wire 7^constituting aconnection between one end of saidfilament and the conductor 4. Said filament is further supported by oneor more wires 9 which are carried by a bead 10 formed on the upper endof an inner bulb 11 which is also supported on the stem 3 by suitablemeans such as a supporting band l2 and supports 13 and 14.

Within the bulb 1l are electrodes 15 and 16 which are described morefully hereinafter, and

17 and 18. The lament 17 is connected at one end with the filament 6 bymeans of a wire 19 and at the other end to the lament 18 by means of awire 20 and resistance 21. The filament 18 is connected by a wire 22with the support 13, the latter being connected to the conductor 5j Whencurrent is supplied to the lamp, it ilows in series through the filament6, filament 17, resistance 2l, and filament 18. The filament 6 heats upto incandescence and provides a source of visible radiation while thefilaments l'l-and 18 heat the electrodes 15 and I16. The potential dropthrough filaments 17 and 18 and resistance 21 is impressed across theelectrodes in any suitable manner, so that the arc is established in theinner bulb 11. It will be understood that the construction thus fardescribed constitutes no part per se of the present invention but isshown merely to illustrate one practical form of lamp to which theinvention may be applied.

As shown more clearly in Fig. 2, the electrodes 15 and 16 each have theform of a tube bent into a U and they are so supported in the inner bulbl1 that the bights of the tubes are adjacent. These electrodes areformed of materials which are substantially non-vaporizabie at operatingtemperatures, and they may be of second-class conductor material, thatis, of material which has high resistance and is substantially anonconductor when cold but which has low 'resistance and becomes a goodconductor on heating. An example of such non-vaporizable second-classmaterial is zirconium oxide. which is preferably molded into the benttube form shown in the drawing to constitute thev electrodes.

It will be understood however that the electrodes may also be formed ofmetal such as tungsten and the like or of any other material which isnon-vaporizabie at operating temperatures, said material being suitablyformed into the U-shaped tubes shown in the drawing. The filaments 17and 18 extend through the tubes and are thus protected from the arc.These tubes may be supported in any suitable manner, and as shown. theends of each tube are provided with supporting bands 23 to which aresecured supports 24 that are fused in the walls of the inner bulb 11. Asclearly shown in Fig. 2. one of the supports 24 of each tube serves as ameans for connecting the heating filament 17 with the filament 6in oneinstance and the heating filament 18 with the support 13 in the otherinstance, and due to this fact. the voltage drop through the heatingfilaments is applied across the electrodes to establish and maintain thearc.

To assist in starting the arc. the electrodes are provided as abovestated with oxides having electronic emission. Preferably these oxidesare located adjacent the ends of the tubes and remoto from the bightsthereof. In this way as the tubes are heated. the electronic emission ofsuch oxides is effective to assist in ionization of the gas or vapor inthe inner bulb and thus to assist in starting the arc. As soon as thearc strikes. however, it establishes and maintains itself on theadjacent bights of the tubes which constitute arcing surfaces. At thesame time, the resistance of the arc path is decreased. most of thecurrent flows through the arc, and the heating filaments 17 and 18 cooloff. The oxides at the ends of the tubes are thus no longer subject tothe full heating of the filaments 17 and i8 and are not affected by thearc itself. the outside of the tubes, as indicated diagrammaticaliy at25, or they may be incorporated with the zirconium oxide during themanufacture of the electrode. The filaments 1'7 and 18 are insulatedfi'om the electrodes in any suitable manner as by coating them with aninsulating cement.

zirconium oxide is particularly suited for use in such electrodesbecause it does not melt or vaporize until temperatures much higher thannormal operating temperatures of the lamp are The oxides may be coatedon4 reached. Thus not only do these electrodes have 'long life, but theydo not evaporate and cause deposits to form on -the walls of the bulb.Substantially no disintegration of such an electrode can be observedafter long periods of operation.

The inner bulb l1 should be of material which transmits the desiredultra-violet radiations produced by the arc. Where mercury or othervapor is employed in the inner bulb which produces radiations shorterthan those desired. the inner bulb 11 may be of any suitable materialwhich absorbs and does not transmit the undesired short waves, or theinner` bulb may be provided with a filter 36 of mica or the like whichdoes not transmit the undesired radiations.

While only one embodiment of the invention has been described andillustrated in the drawing, it is to be expressly understood that theinvention is not limited thereto but is capable of considerablevariation. Moreover, the use of the novel electrode is not restricted tothe particular type of lamp shown in the drawing, but may be employed inany electric arc lamp either with or without the incandescent filament6. Furthermore. many of the advantages of the invention can be obtainedwith the heating filaments outside the electrodes, which in such caseneed not be hollow; and similarly as respects many features of theinvention the electrodes need not be of second-class conductor materialbut may be of any substantially non-vaporizable material. Thereforereference is to be had to the appended claims for a. definition of thelimits of the invention.

What is claimed is:

1. An electric arc lamp comprising apair of U-shaped electrodes disposedwith their bight portions adjacent, said bight portions comprisingarcing surfaces of material substantially nonvaporizabie during arcoperation and the legs of said electrodes including an oxide having highelectronic emission 'when heated, means for supplying potential to saidelectrodes, and means for heating said electrodes to start the are.

2. An electric arc lamp comprising a pair of hollow U-shaped electrodesdisposed with their 'bight portions adjacent, said bight portionsoomprising arcing surfaces of material substantially non-vaporizableduring arc operation and the legs of said electrodes including an oxidehaving high electronic emission when heated. heating filaments withinsaid hollow electrodes, and means for energizing said filaments andelectrodes.

3. An electric arc lamp comprising a pair of U-shaped electrodesdisposed withtheir bight portions adjacent. said bight portionscomprising arcing surfaces of material substantially nonvaporizableduring arc operation and the legs of said electrodes including an oxidehaving high electronic emission when heated, means for energizing saidelectrodes. and electrode heating means connected in parallel with saidelectrodes.

4. An electric arc lamp comprising a pair of hollow U-shaped electrodesdisposed with their bight portions adjacent. said bight portionscomprising arcing surfaces of material substantially non-vaporizableduring arc operation and the legs of said electrodes including an oxidehavin;r high electronic emission when heated. means for energizing saidelectrodes, and heating filaments within said electrodes, said heatingfilaments being connected in series with one another and in parallelwith said electrodes.

5. An electric arc lamp comprising a pair of hollow U-shaped electrodesdisposed with their bight portions adjacentsaid bight portionscomprising arcing surfaces of zirconium oxide and the legs of saidelectrodes including one or more oxides having high electronic emissionwhen heated, means for supplying potential to said electrodes, andheating filaments Within said electrodes, said filaments being connectedin series with each other and in parallel with said electrodes.

6. An electrode of the class described comprising a U-shaped member ofsecond class conductor material, the bight portion of said membercomprising an arcing surface which is substantially non-vaporizableduring arc operation, the legs o said member including an oxide havingan arcing surface and the legs of said element having 'incorporatedtherein an oxide having high electronic emission when heated.

GEORGE SPERTI.

